This invention relates to a system allowing an operator to input control signals to an engine control for assisting the shifting of a transmission between several speeds.
Heavy vehicles are typically driven with a multi-speed transmission transmitting drive from an engine to the axles for the vehicle. The transmission is movable through several speeds at the control of a manual stick shift.
In a typical transmission, a number of gears inter-engage to provide the several speeds. In a typical manual transmission, toothed shift collars slide to engage selected gears with an output shaft. To complete a shift, the operator must first move the gear that is presently engaged out of engagement to a "neutral" position. In the neutral position, the transmission does not engage any gear, and thus rotational drive is not transmitted to the transmission output shaft from the input of the engine.
The movement from an engaged position to a neutral position must occur while the gears are engaged. When the gears are engaged rotational drive is being transmitted from the engine to the transmission. The gears and collar actually transmitting rotational drive carry a high torque load, which makes it difficult if not impossible for an operator to manually move the collar out of engagement. This is a phenomena called "torque lock." To overcome torque lock, most modern vehicles are equipped with clutches. An operator is able to break the torque lock by actuating a clutch pedal, thus breaking the drive connection between the engine and the transmission. The operator is then able to easily move the gear out of engagement. Alternatively, the driver may be able to reduce torque sufficiently through the accelerator pedal, although this requires a good deal of experience.
In heavy vehicles, the clutching necessary to complete a shift between gears is relatively complicated. Typically, the driver must actuate or disengage the clutch and move the transmission to neutral. The clutch is then reengaged. The operator then modifies engine speed through the accelerator to synchronize the speed ratio to that necessary at the next gear. The operator must then manually move the gear shift lever to engage the gear in the proper new gear. Typically, an operator is not able to identically match the synchronization speed ratio, and must actuate the clutch to engage the new gear.
All of these steps make gear shifts complicated. This is particularly true when several shifts are to be made in quick succession. More recently, heavy vehicles have become equipped with controls and operator-intensive operations. Thus, it would be desirable to reduce the steps an operator must make on a routine basis when driving. To this end, it would be desirable to allow the operator to move the gear out of engagement for a shift without having to operate the clutch, synchronize the speed ratio and then reengage the transmission in the new gear, again without having to use the clutch.
The prior art has proposed systems to assist in eliminating the torque load on the vehicle when attempting to move the gear to neutral. Those systems have been somewhat impractical, and have not provided an operator the option of not using the torque elimination feature. A more experienced driver may wish to not use the torque elimination feature, but may sometimes choose to use the clutch, or use the accelerator to reduce engine power. A more experience driver may only be interested in using the torque elimination feature when several sequential shifts are to be made. Thus, the prior system which does not provide the operator the option of not using the torque elimination on a gear shift has deficiencies.
Moreover, the prior art does not allow the operator to provide an indication of the shift direction to the engine control. Since the prior art does not receive a signal from the driver to indicate whether an upshift or downshift is next occurring, the prior art must somehow predict which gear will be next when determining a synchronization speed. This is somewhat undesirable, and may not allow the system to operate as quickly as a system in which the operator provides an indication of the direction of the next expected gear shift.